During the past decade, repositionable products, such as Post-it.RTM. Notes and related products, commercially available from 3M Co., have become virtually indispensable consumer and business office items. The commercial success of these products can be attributed to repositionable, elastomeric, polymeric microsphere adhesives, see for example, U.S. Pat. Nos. 3,691,140 and 4,166,152.
Typically, coating such microsphere adhesives onto paper is accomplished by using a direct coating process. However, stripe coating of water-based adhesives onto paper is often difficult and produces unsatisfactory results due to paper distortions. One way of avoiding paper distortion, or as it is often referred to "cockling" is to transfer coat dry adhesive as stripes.
Although transfer coating (indirect coating) of adhesive is generally known, see for example U.S. Pat. No. 3,121,021, problems associated with coating a particulate or particulate-containing adhesive (such as a microsphere or microsphere-containing adhesive) have not been recognized in the art dealing with film forming adhesives.
Some sheet-to-sheet coating process, which continuously coat a pseudo-web of overlapping paper sheets, use water-based adhesives. The adhesives are coated onto a silicone belt. The adhesive is then dried (either partially or fully) on the belt and transferred to the pseudo-web of sheets. However, the adhesive materials used do not satisfactorily transfer cleanly and with consistency. Various solutions have been proposed to aid in transferring adhesives from a coating intermediate carrier to a moving web, but to date all have been relatively unsuccessful.
Although microsphere adhesive formulations including binder, surfactant and thickeners are known, formulations which meet the special transfer coating process needs (as enumerated above), are not known.